Here's a happy farmyard scene, discovered on the branch of a pussy willow tree as I pruned it. Click the picture for a larger version so you can see the detail! I hadn't seen aphids as exotically liveried as this before, being more familiar with plain green or black versions. The twin orange 'horns' on the rear of each one are called cornicles and it seems the jury is still out on exactly what they're for.

The ants in attendance are literally farming these aphids, stroking them and then consuming the sweet honeydew secretions that come from their rear ends. The ant on the far right is clearly stroking that aphid with a front leg. Also if you look closely, the very left-most aphid is a bit bigger and has wings. They don't fly well though, relying mostly on the wind to carry them decent distances.